The hand lowered with the palm facing outward is the gesture of bestowing blessings or of giving charity. The hand is extended downward, palm out. Mostly on standing Buddha images, but sometimes also represented in the sitting position.

Blessing

(with sitting or standing posture)The right hand is pending in vada mudra. When standing the left hand will clasp the edge of the monastic robe.No particular story attached. It denotes the altruistic quality of the Buddha.